Relèvements des revêtements de courbes faiblement ramifiés

Let X be a smooth projective curve over a perfect field of characteristic p>0 and G a finite group of automorphism of X. Let ν(X,G) be the characteristic of the versal equivariant deformation ring R(X,G) of (X,G). When the ramification is weak (i.e., all second ramification groups are trivial), we prove that ν(X,G) ∈ {0,p} and we compute R(X,G).

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Résumé Soit X une courbe projective lisse sur un corps parfait de caractéristique p>0 et G un groupe fini d'automorphismes de X. Nous considérons la caractéristique ν(X,G) de l'anneau versel R(X,G) de déformations équivariantes de (X,G). Dans le cas d'une ramification faible (où tous les seconds groupes de ramification sont triviaux), nous démontrons que ν(X,G) ∈ {0,p} et nous calculons R(X,G).

     

Über 2,4-Difluorzimtsäure

Zusammenfassung Aus 2,4-Difluortoluol wurden nach üblichen Methoden 2,4-Difluorbenzaldehyd und 2,4-Difluorzimtsäure hergestellt.     

Hydrogen in perovskites: Mechanism of solubility, chemical state, effect on electron subsystem, phase transformation

The phenomena of hydrogen/water solubility in YBa₂Cu₃O_7-δ and BaCeO₃ undoped and doped by Y and Nd are considered. New experimental data as well as recently published data have been accumulated to discuss the chemical state of protons, taking into account the fairly strong interaction of the protons with the electron subsystem. Phase transformation of the studied oxides induced by hydrogen/water intercalation were revealed by the investigations of thermal effects, X-ray diffraction, Raman spectroscopy, inelastic neutron scattering and nuclear quadrupole resonance. Paper presented at the 5th Euroconference at Solid Statre Ionics, Benalmádena, Spain, Sept. 13–20, 1998.     

Intramolekulare diels-alder-reaktionen mit substituierten 1,2,4,5-tetrazinen und 1,2,4-triazinen

1,2,4,5-tetrazines as well as 1,2,4-triazines carrying sidechain dienophiles react in an intramolecular Diels-Alder cycloaddition with inverse electron demand to yield novel bicyclic pyridazines and pyridines.     

The mössbauer effect: A potentially ideal probe into Brownian motion

We calculate the Mössbauer spectrum of nuclei embedded in spheres of radius on the order of 1 μm which are suspended in a liquid. We demonstrate that the Mössbauer effect is an ideal means for testing the deductions based upon a generalized Langevin equation which takes into account the effects of acceleration memory on the force and torque of the liquid on a sphere and for studying, generally, the detailed statistical dynamical behavior of Brownian particles. The spectrum is expressed in terms of an integral over an integrand consisting of standard functions. Experimental desiderata are discussed and a list of sample experimental parameters given.